A case-control study of the association of previous infection with Chlamydia trachomatis (CT), and douching with ectopic pregnancy (EP), will be performed. Serum and detailed interview data will be collected from women who have had an EP in San Francisco, Los Angeles, New York, and Pittsburgh. Controls will be pregnant women in their first and second trimesters matched to EP cases on the basis of race and age (+/- one year) within each site. Prior exposure to CT will be determined by serologic tests. Matched pair analysis will be performed as well as conditional logistic regression analysis confounders including age, race past history of infertility, pelvic inflammatory disease (PID), sexually transmitted diseases (STD), intrauterine device (IUD) usage, and douching practices.